Method for automatically obtaining a quiet zone of a microwave anechoic chamber

Abstract

The present application relates to a kind of microwave darkroom static area automatic acquisition method, microwave darkroom static area is under the static area of reflectivity level and amplitude unevenness;The static area under reflectivity level is obtained using initial seed point selection algorithm and growth algorithm;The automatic acquisition of amplitude unevenness index range is based on the reflectivity level range, by selecting amplitude unevenness standard point as initial seed point, also in the way of neighborhood growth;The calculation of amplitude unevenness growth process only needs to extract its amplitude from the previous reflectivity level calculation result, and compare with standard point amplitude;Static area is the spatial range under the superposition of two indicators.The present application realizes the static area of the required static area index three-dimensional space, realizes static area extraction automation.

Description

Technical Field

[0001] This invention relates to a method for automatically acquiring the quiet zone of a microwave anechoic chamber, belonging to the field of electromagnetic modeling technology. Background Technology

[0002] Microwave anechoic chambers are mainly used for antenna performance measurement, target RCS characteristic measurement, and electromagnetic compatibility measurement. The quiet zone is the area within the anechoic chamber where clutter interference is minimal; placing the device under test (DUT) within the quiet zone improves testing efficiency. However, microwave anechoic chambers are expensive to construct, making simulation and modeling of the chamber particularly important.

[0003] The extent, location, and shape of the quiet zone depend on factors such as the shape, size, operating frequency, and absorbing materials of the microwave anechoic chamber. Therefore, it is essential to automatically acquire the quiet zone whenever its performance changes during simulation. Currently, researchers' attention in anechoic chamber simulation mainly focuses on how to build models, how to improve absorbing materials, and how to accurately measure the field strength distribution within the anechoic chamber. The method used to acquire the quiet zone's extent is to manually estimate it using the sampling results of a planar array by creating cross-sections.

[0004] The location and size of the cross-section in the darkroom are determined by human experience. This process relies excessively on the researcher's experience and knowledge, and it is difficult to intuitively present the three-dimensional still area. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a method for automatically acquiring the quiet zone of a microwave anechoic chamber, the specific technical solution of which is as follows: A method for automatically acquiring the quiet zone of a microwave anechoic chamber includes the following steps: Step 1: Build a microwave anechoic chamber simulation environment and perform meshing on the microwave anechoic chamber; Step 2: Select the midpoint of the line segment at the intersection of the emission source direction and the microwave anechoic chamber model as the seed point to be determined, and add the seed point to the queue of undetermined points; Step 3: Determine whether the seed point in the pending queue meets the reflectivity level index. If it does, it means that the seed point has been found and proceed to step 10. If it does not meet the index, proceed to step 4. Step 4: Clear the pending queue, use the binary search method to select points on the line segment as pending seed points, and add the pending seed points to the pending queue; Step 5: Cutoff condition for selecting points on the line segment. Is the distance between the two points intercepted by the bisection method less than the microwave anechoic chamber grid spacing? If not, return to step 3; if not, proceed to step 6. Step 6: Divide the microwave anechoic chamber model, take the center point of each divided model as the seed point to be determined, and add the seed point to the queue of undetermined points; Step 7: Determine whether the seed points in the pending queue meet the reflectivity level index. If they do, proceed to step 10; otherwise, proceed to step 8. Step 8: Determine whether the minimum side length after model segmentation is less than the microwave anechoic chamber grid spacing. If it is less, the program ends; if it is not less, continue to step 6. Step 9: Seed point not found, determining that there is no quiet zone in the darkroom, program ends; Step 10: Generate neighborhood coordinates from the seed point, add the neighborhood coordinates to the pending queue, and add the seed point to the result list; Step 11: Calculate the reflectivity level of the seed points in the pending queue, and determine whether there is a next-generation seed point. If there is no next-generation seed point, it means that the quiet zone under the reflectivity level has been found, and proceed to step 12; if there is a next-generation seed point, proceed to step 10. Step 12: Select a coordinate point from the results list as the standard point for amplitude unevenness; Step 13: Using the growth method of generating neighborhood coordinate points from the seed point, take the difference between the amplitude of the neighborhood points and the standard point, and put the points that meet the amplitude unevenness requirements into a new result list; Step 14: Process complete.

[0006] Furthermore, the microwave anechoic chamber quiet zone is a quiet zone under two indicators: the quiet zone under reflectivity level and the quiet zone under amplitude unevenness. The quiet zone at the reflectivity level is obtained using the initial seed point selection algorithm and the growth algorithm; The specific process of the first-generation seed point selection algorithm is as follows: In the entire dark room, the initial seed point that meets the standard reflectivity level requirement is obtained by calculating the seed point selection method rules. The quiet zone boundary is explored outward from the seed point as the center. The outward exploration process is to grow the neighboring coordinate points with the three-dimensional coordinate point of the seed point as the center, and then calculate their reflectivity level. The automatic acquisition of the amplitude unevenness index range is based on the reflectivity level range. By selecting a standard point of amplitude unevenness as the initial seed point, growth is also performed in a neighborhood manner. The calculation of the amplitude unevenness growth process only requires extracting the amplitude from the previous reflectivity level calculation result and comparing it with the amplitude of the standard point. The quiet zone is the spatial range under the superposition of the two indices.

[0007] Furthermore, the darkroom is meshed based on the triangulation data of the darkroom model, with a mesh interval of 0.01 times the minimum side length of the bounding box of the darkroom model.

[0008] Furthermore, there are two schemes for selecting the initial seed point. Scheme 1 is to take the point on the orientation of the emission source. On the line segment of the intersection of the emission source and the anechoic chamber model, the three-dimensional coordinate point is continuously taken as the seed point to be determined and its field value is calculated until the seed point that satisfies the reflectivity level is found. The bisection method is continuously divided into line segments. When the divided line segment is smaller than the side length of the microwave anechoic chamber grid, it stops. If no seed point is found using Scheme 1, Scheme 2 is adopted. Scheme 2 involves dividing the microwave anechoic chamber and taking the center point of each small cube after division as the seed point to be determined. The process of continuous division is similar to the division method of an octree. The constraint is that the side length of the small cube after division must not be less than the side length of the grid.

[0009] Furthermore, the process of generating neighborhood coordinate points from the seed point is a process of expanding outwards from the grid length. Each seed point is located at the center of a cube with a grid side length twice that of the cube in the simulation, and the generated neighborhood coordinate points are the center points of the six faces of the cube.

[0010] Furthermore, the meshing process in step 1 involves processing the subdivision data of the bottom layer of the microwave anechoic chamber bounding box before generating seed points, to obtain six data points for the microwave anechoic chamber bounding box model in the Cartesian coordinate system: x_min, x_max, y_min, y_max, z_min, and z_max, with the minimum side length d = min(abs(x_max-x_min), abs(y_max-y_min), abs(z_max-z_min)).

[0011] Furthermore, the meshing process is to ensure that each three-dimensional point is taken on the mesh. Each obtained three-dimensional point is corrected, and points that are not on the mesh are corrected to their nearest mesh. Moreover, when calculating the quiet zone under the amplitude unevenness standard, the previously calculated field value can be obtained from the coordinate point index in the calculation result of the reflectivity level.

[0012] The beneficial effects of this invention are: This invention realizes the three-dimensional space of the quiet zone under the required quiet zone parameters (reflectivity level and field uniformity), and automates the quiet zone extraction. This invention can be applied to the field of microwave anechoic chamber simulation and has broad application prospects. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the structure of the present invention, which takes three-dimensional coordinate points at the intersection of the direction of the emission source and the anechoic chamber model.

[0014] Figure 2 This is a schematic diagram of the structure of the present invention for obtaining three-dimensional coordinate points by dividing a darkroom model.

[0015] Figure 3This is a schematic diagram of the process for automatically acquiring the quiet zone of a microwave anechoic chamber according to the present invention.

[0016] Figure 4 This is a schematic diagram of the structure of the present invention that grows neighborhood coordinates from a seed point.

[0017] Figure 5 This is a schematic diagram of the automatic extraction result structure in the rectangular darkroom example of the present invention. Detailed Implementation

[0018] The invention will now be described in further detail with reference to the accompanying drawings.

[0019] This invention provides a method for automatically acquiring the quiet zone in a microwave anechoic chamber. During microwave anechoic chamber simulation, the automatic acquisition method provided by this invention can realize the three-dimensional space of the quiet zone under the required quiet zone (reflectivity level and field uniformity) indicators, thereby automating the quiet zone extraction.

[0020] Figure 1 The diagram illustrates the structure of this invention, which uses a three-dimensional coordinate point at the intersection of the transmitter's orientation and the anechoic chamber model. In the case of a single antenna and a single frequency, the quiet zone is most likely to appear in the antenna's orientation. Therefore, on the line segment at the intersection of the antenna's orientation and the anechoic chamber model, the nearest grid point of the three-dimensional coordinate point is continuously bisected as a seed point for calculation. This iterative process stops when a seed point is found. The cutoff condition for Scheme 1 is when the distance between the two selected coordinate points is less than the grid length.

[0021] Figure 2 The diagram illustrates the structure of this invention for obtaining 3D coordinate points by segmenting an anechoic chamber model. In Scheme 1, no seed point is found in the antenna's orientation. Therefore, the anechoic chamber model is segmented, and the center point is used as a potential seed point. When the field value at the center point does not meet the quiet zone requirement, the model is further segmented. The center point of each segmented small cube is again used as a potential seed point for calculation. If a quiet zone is still not found, each small cube is segmented again. Segmentation stops when a seed point is found. The cutoff condition for Scheme 2 is when the side length of the segmented cube is less than the mesh length.

[0022] Figure 3 The diagram shows the automatic acquisition process of the quiet zone in a microwave anechoic chamber according to the present invention. For example, when the required quiet zone reflectivity level is less than -40dB and the required amplitude unevenness is fluctuation not exceeding 0.25dB, a typical rectangular anechoic chamber model is selected, with a size of 20*20*20m and the midpoint of the bottom surface located at (0, 0, -7). A 1.575GHz antenna is selected as the transmitting source, and the absorbing material is set to a -45dB equivalent plane. The automatic acquisition process of the quiet zone in this anechoic chamber is as follows: Step 301: Build a microwave anechoic chamber simulation environment and mesh the microwave anechoic chamber. The mesh size of this rectangular microwave anechoic chamber is 0.2m. Step 302: Select the midpoint of the line segment at the intersection of the direction of the transmitting source and the microwave anechoic chamber model as the seed point to be determined, and add the seed point to the queue of undetermined points. The antenna position is (0, 0, 13.5), the antenna orientation is downward along the axis, and the power is 0.499W. Step 303: Determine whether the seed point in the pending queue meets the reflectivity level index. If it does, it means that the seed point has been found and proceed to step 310. If it does not meet the index, continue to step 304. Step 304: Clear the pending queue, use the binary search method to select points on the line segment as pending seed points, and add the pending seed points to the pending queue; Step 305: Cutoff condition for selecting points on the line segment. Is the distance between the two points intercepted by the bisection method less than the microwave anechoic chamber grid spacing? If not, return to execute 303; if not, execute 306. Step 306: Divide the microwave anechoic chamber model, take the center point of each divided model as the seed point to be determined, and add the seed point to the queue to be determined; Step 307: Determine whether the seed points in the pending queue meet the reflectivity level index. Select -40dB as the standard quiet zone reflectivity level. If it meets the index, proceed to step 310; otherwise, proceed to step 308. Step 308: Determine whether the minimum side length after model segmentation is less than the microwave anechoic chamber grid spacing. If it is less, the program ends; if it is not less, continue to step 306. Step 309: If the seed point is not found, it is determined that there is no quiet zone in the darkroom, and the program ends; Step 310: Generate neighborhood coordinates from the seed point, add the neighborhood coordinates to the pending queue, and add the seed point to the result list; Step 311: Calculate the reflectivity level of the seed points in the pending queue. Is there no next-generation seed point? If not, it means the quiet zone under the reflectivity level has been found, and proceed to step 312; if there is still a next-generation seed point, proceed to step 310. Step 312: Select a coordinate point from the results list as the standard point for amplitude unevenness. In this case, (0, 0, 3.2) is selected as the standard point. Step 313: Using the same growth method, take the difference between the amplitude of the neighboring points and the standard point, and put the points that meet the amplitude unevenness requirements into a new result list. In this case, the amplitude unevenness standard is that the amplitude fluctuation should not be greater than 0.25dB. Step 314: Process complete.

[0023] Figure 4The diagram shows a schematic of the structure of this invention that grows neighborhood coordinates from a seed point. The seed point is located in the middle of the cube, pointing to the center of the six faces of the cube. The center of each of the six faces is the three-dimensional coordinate point to be calculated that is grown from this seed point.

[0024] Figure 5 The diagram shows the quiet zone space automatically obtained by the present invention under the rectangular anechoic chamber. It is the area of ​​the entire rectangular anechoic chamber where the reflectivity level is less than -40dB and the amplitude unevenness is ±0.25dB.

[0025] In summary, this invention provides a method for automatically acquiring the quiet zone of a microwave anechoic chamber. This technology can be applied to the field of microwave anechoic chamber simulation. For example, when using a microwave anechoic chamber to measure radio frequency devices, target scattering characteristics, and other equipment, this technology can be used to automatically acquire the quiet zone of the microwave anechoic chamber. Therefore, this technology has high promotional value.

[0026] This invention provides a method for automatically acquiring the quiet zone of a microwave anechoic chamber. There are many methods and approaches to implement this technical solution. The above is only a preferred embodiment of this invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this invention, and these improvements and modifications should also be considered within the scope of protection of this invention.

[0027] Based on the above-described preferred embodiments of the present invention, and through the above description, those skilled in the art can make various changes and modifications without departing from the technical concept of the present invention.

Claims

1. A method for automatically acquiring the quiet zone of a microwave anechoic chamber, characterized in that: Includes the following steps: Step 1: Build a microwave anechoic chamber simulation environment and perform meshing on the microwave anechoic chamber; Step 2: Select the midpoint of the line segment at the intersection of the emission source direction and the microwave anechoic chamber model as the seed point to be determined, and add the seed point to the queue of undetermined points; Step 3: Determine whether the seed point in the pending queue meets the reflectivity level index. If it does, it means that the seed point has been found and proceed to step 10. If it does not meet the index, proceed to step 4. Step 4: Clear the pending queue, use the binary search method to select points on the line segment as pending seed points, and add the pending seed points to the pending queue; Step 5: Cutoff condition for selecting points on the line segment. Is the distance between the two points intercepted by the bisection method less than the microwave anechoic chamber grid spacing? If not, return to step 3; if not, proceed to step 6. Step 6: Divide the microwave anechoic chamber model, take the center point of each divided model as the seed point to be determined, and add the seed point to the queue to be determined. Step 7: Determine whether the seed points in the pending queue meet the reflectivity level index. If they do, proceed to step 10; otherwise, proceed to step 8. Step 8: Determine whether the minimum side length after model segmentation is less than the microwave anechoic chamber grid spacing. If it is less, the program ends. If it is not less than, continue to step 6; Step 9: Seed point not found, determining that there is no quiet zone in the darkroom, program ends; Step 10: Generate neighborhood coordinates from the seed point, add the neighborhood coordinates to the pending queue, and add the seed point to the result list; Step 11: Calculate the reflectivity level of the seed points in the pending queue, and determine whether there is a next-generation seed point. If there is no next-generation seed point, it means that the quiet zone under the reflectivity level has been found, and proceed to step 12; if there is a next-generation seed point, proceed to step 10. Step 12: Select a coordinate point from the results list as the standard point for amplitude unevenness; Step 13: Using the growth method of generating neighborhood coordinate points from the seed point, take the difference between the amplitude of the neighborhood points and the standard point, and put the points that meet the amplitude unevenness requirements into a new result list; Step 14: Process complete.

2. The method for automatically acquiring the quiet zone of a microwave anechoic chamber according to claim 1, characterized in that: The microwave anechoic chamber quiet zone is the quiet zone under two indicators: the quiet zone under reflectivity level and the quiet zone under amplitude unevenness. The quiet zone at the reflectivity level is obtained using the initial seed point selection algorithm and the growth algorithm; The specific process of the first-generation seed point selection algorithm is as follows: In the entire dark room, the initial seed point that meets the standard reflectivity level requirement is obtained by calculating the seed point selection method rules. The quiet zone boundary is explored outward from the seed point as the center. The outward exploration process is to grow the neighboring coordinate points with the three-dimensional coordinate point of the seed point as the center, and then calculate their reflectivity level. The automatic acquisition of the amplitude unevenness index range is based on the reflectivity level range. By selecting a standard point of amplitude unevenness as the initial seed point, growth is also performed in a neighborhood manner. The calculation of the amplitude unevenness growth process only requires extracting the amplitude from the previous reflectivity level calculation result and comparing it with the amplitude of the standard point. The quiet zone is the spatial range under the superposition of the two indices.

3. The method for automatically acquiring the quiet zone of a microwave anechoic chamber according to claim 1, characterized in that: The darkroom is meshed based on the triangulation data of the darkroom model, with a mesh interval of 0.01 times the minimum side length of the bounding box of the darkroom model.

4. The method for automatically acquiring the quiet zone of a microwave anechoic chamber according to claim 1, characterized in that: There are two schemes for selecting the initial seed point. Scheme 1 is to take the point on the orientation of the emission source. On the line segment of the intersection of the emission source and the anechoic chamber model, the three-dimensional coordinate point is continuously taken as the seed point to be determined and its field value is calculated until the seed point that satisfies the reflectivity level is found. The bisection method is continuously divided into line segments. When the divided line segment is smaller than the side length of the microwave anechoic chamber grid, it stops. If no seed point is found using Scheme 1, Scheme 2 is adopted. Scheme 2 involves dividing the microwave anechoic chamber and taking the center point of each small cube after division as the seed point to be determined. The process of continuous division is similar to the division method of an octree. The constraint is that the side length of the small cube after division must not be less than the side length of the grid.

5. The method for automatically acquiring the quiet zone of a microwave anechoic chamber according to claim 1, characterized in that: The process of generating neighborhood coordinates from a seed point is an outward expansion of the grid length. Each seed point is located at the center of a cube with a grid side length twice that of the cube in the simulation, and the generated neighborhood coordinates are the center points of the six faces of the cube.

6. The method for automatically acquiring the quiet zone of a microwave anechoic chamber according to claim 1, characterized in that: The meshing process in step 1 involves processing the meshing data of the bottom layer of the microwave anechoic chamber bounding box before generating seed points, to obtain six data points for the microwave anechoic chamber bounding box model in the Cartesian coordinate system: x_min, x_max, y_min, y_max, z_min, and z_max. The minimum side length d = min(abs(x_max-x_min), abs(y_max-y_min), abs(z_max-z_min)).

7. The method for automatically acquiring the quiet zone of a microwave anechoic chamber according to claim 1, characterized in that: The meshing process is to ensure that each three-dimensional point is taken on the mesh. Each obtained three-dimensional point is corrected, and points that are not on the mesh are corrected to their nearest mesh. Moreover, when calculating the quiet zone under the amplitude unevenness standard, the previously calculated field value can be obtained from the coordinate point index in the calculation result of the reflectivity level.

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